1. Field of the Invention
The present invention relates to a method of producing a web of plurality of interconnected plastic bags with longitudinal gusset folds, at least comprising a central and two outer longitudinal gusset fold edges which bound a first and a second gusset fold part, by providing a continuously supplied tubular plastic foil by heatsealing with a first transverse bottom seal which extends across the entire width of the tubular foil and moving the tubular foil over a predetermined distance to another sealing position.
2. Description of the Prior Art
A method of this type has been used in the prior art. In the prior art methods the first transverse bottom seal is produced by heatsealing the various different foil layers across the entire width of the bag after having applied first and second fold part seals slopingly extending with respect to one another, preferably under an angle of 45.degree., at both ends of the bag.
The first fold part seals contact the first transverse bottom seal so that a filled bag can be given a block shape at the bottom side. The second fold part seals likewise form, together with a final heatseal to be applied, a block bottom, thus causing a filled bag to have a block shape at either side.
The difficulty with the said prior art method is, that it is inappropriate, as the quality of the first transverse bottom seal leaves much to be desired, which is inherent with the fact that in a heatsealing process two foil layers have to be heatsealed to each other in the central part of a tubular foil web, whilst four foil layers have to be heat-sealed to each other in gusset fold parts. Especially the transition from the two-layer-seal toward the four-layer-seal will involve problems and particulary a weakening of the foil material.